Temperature-controlled apparatus



Nov. 18, 1958 R. MOORE TEMPERATURE-CONTROLLED APPARATUS Filed April 22, 1957 my G m .II 6.40. N F

THERMHLL Y REsPo/vs/vs B/ME TnL SILVER sun INVENTOR ROBERT L- MOORE United States Patent Robert L. Moore, Mansfield, Ohio, asslgnor to Westiughouse Electric Corporation, East Pittsburgh, Pa., a corporatiou of Pennsylvania ApplicatiouApril 22, 1957,"Serial No. 654,137 2 Claims. (Cl. 200-138) This invention relates to thermostatic devices, particularly to temperature-responsive switches of the type utilizing a bimetallic snap-acting disc and a movable contact structure coupled thereto. An object of the invention is to provide improved apparatus of this kind.

Thermostatic devices'of the class set forth and proposed heretofore have, in many cases, an objection in that the positional relationship between the bimetal disc and its movable contact has varied during heating and cooling of the bimetal. Accordingly, the accuracy of the device may be adversely affected. Another object of the invention is to maintain proper positioning of the bimetal disc relative the movable contact coupled thereto, throughout the range of temperatures to which the bi metal is subjected.

Another object of the present invention is to insure that movement of the bimetal relative the stationary contacts will remain substantially constant throughout relatively long periods of use.

It is another object to provide a bimetal for biasing a movable contact relative stationary contacts such that the full force of the bimetal will be exerted upon the movable contact.

A further object of the present invention is to provide a switch of the type set forth in which the components may be easily assembled and disassembled.

' One embodiment of the present invention provides a ceramic base through which a stud member extends. At one end of the stud, a bimetallic disc is mounted and carries an annular retainer adjacent its outer periphery. The retainer secures the bimetallic member to a movable contact disc by a plurality of finger-like portions provided on the retainer ring. The movable contact disc is held in predetermined spaced relation with a pair of stationary contacts during the open position of the switch and bridges the contacts in the switch closed portion. The retainer ring is aseparate element and the expansion and contraction of the bimetallic disc does not affect the connection between the bimetallic disc and the movable contact disc.

The foregoing and other objects are effected by the invention as will be apparent from the following description and claims taken in conection with the accompanying drawings, forming a part of this application, in which:

Fig. l is a plan view of a switch constructed in accordance with the present invention;

Fig. 2 is a section taken along the line IIII of Fig. 1, looking in the direction indicated by the arrows, showing the device of Fig. l in the closed position;

Fig. 3 is a view illustrating the device in the open position and is partly in elevation and partly in section; and

Fig. 4 is a fragmentary plan view, similar to Fig. 1, illustrating a modified embodiment of the present invention.

Referring to the drawing in detail and in particular to Figs. 1 and 2, there is illustrated a thermostatic switch comprising an annular housing 11 constructed of a ceramic material closed at one end by a planar end wall or base "ice 12 and open at the other end. Centrally disposed in the base 12 is a sleeve 14 having internal threads and formed with an integral shoulder 16 disposed in a recess in the bottom of the base 12. The sleeve 14 is provided with an extending portion or flange 17 which, after the sleeve is inserted inlthe base, is turned at a right'angle to the longitudinal axis of the sleeve, over a washer 18, thereby securing the sleeve to the base. A rod or stud 19 is threaded in the sleeve 14 and is provided with a lock nut 21 adjacent the shoulder 16. I

The upper end portion of the stud 19 is provided with an outwardly extending flange 23 and a head 24, the latter being spaced from the flange 23 so as to provide an annular recess 26. The head 24 is hollow to receive the stud 19 and is secured thereto by peening over a portion 27 of the stud. In the recess 26, there is centrally mounted a thermally responsive bimetallic disc 28 having a central mounting hole, larger in diameter than thediameter of the stud at the recess. The axial dimension of the recess 26 and the diameter of the mounting hole in the bimetallic disc provide clearance to permit the bimetallic disc 28 to flex freely as hereinafter described.

The bimetallic disc 28 is provided at its outer periphery with an annular retainer or ring member 29, preferably of resilient material. Referring to Figs. 2 and 3, the the retainer 29 is provided with a concave or spherical surface 30 in contact with the bimetallic disc 28. The retainer 29 is further provided with a rim having a plurality of fingerlike projections 31. The fingers 31 have axial portions 31a extending parallel to the longitudinal axis of the stud 19 and radial portions 31b extending inwardly. The axial portions 31a of the fingers 31 carry a dished contact disc 32, having a current carrying lamina 33, in a coaxial relationship with the bimetallic disc 28. The contact disc 32 is provided with a central mounting opening, larger in diameter than the diameter of the stud, so that it is free to move along the longitudinal axis of the stud. The fingers 31 couple or secure the contact disc 32 to the bimetallic disc 28 adjacent their peripheries. The resilient radial portions 31b bias the contact disc 32 and the bimetallic disc 28 toward the spherical surface 30 and are so formed that only the radially innermost margin contacts the lamina 33.

As best shown in Figs. 2 and 3, the peripheral portions of the discs 28 and 32 are retained in engagement at all times, with the result that warping or sagging of the bimetallic disc 28 is prevented. The contact disc is provided with an annular embossed portion 34 for bridging a plurality of stationary contacts 36 in the closed position of the switch. The stationary contacts 36 are provided with respective stationary terrni nals 38. By manually rotating the contact disc 32 with respect to the bimetallic disc 28, different portions of the boss 34 are brought into contact with the stationary contacts 36, thereby prolonging their life.

In the preferred embodiment, the thermally responsive bimetallic disc 28 is constructed with its upper lamina, as viewed in Figs. 2 and 3, formed o f.low expansion material and the lower lamina of high expansion material. The disc is suitably bowed so that, at predetermined temperatures, the disc will snap from one stable position through a position of instability to its other stable position, as is understood. The switch is constructed and the bimetallic disc 28 positioned so that, when the disc is relatively cool, the lamina 33 of the contact disc 32 is in abutment with the stationary contacts 36. The bimetallic disc 28, when in the closed position, has a portion of its top surface abutting the bottom of the head 24 and its bottom surface elevated above the flange 23. The top surface of the bimetallic disc is now inbefore-describedconvex surface 30 of the retainer 29.

Patented Nov. 18, 1 958 When the bimetallic disc is heated, it expands and becomes progessively stressed until it flexes or snaps to its reverse position causing the mid-portion of the bottom surface of the bimetallic disc 28 to move away from the head 24 and abut the top of the flange 23. Thus, the contact disc 32 is transported upwardly away from the stationary contacts 36; As is well known, the response characteristic of this type of switch may be varied by axially adjusting the stud 19 so that the stress in the bimetallic disc 28 is varied, causing the latter to snap at a different temperature.

Referring to Fig. 4 in detail, a modification of the switch is illustrated generally similar to the switch illustrated in Figs. 1 through 3, except that the contact disc is provided with ears 51 which prevent the contact disc from rotating. The cars 51 extend radially outwardly between two of the finger-like projections 53. The earsv5l engage suitable vertically extending grooves 56 located in the annular housing 58. Figure 4 illustrates only one car 51 and groove 56 but another diametrically opposite ear and groove 56 may be provided. In this instance, the current carrying surface, indicated by the dotted line 59 (similar to surface 33 of the previous embodiment) need be only in the form of a strip for bridging the stationary contacts.

The device of the subject invention has special application where a physically small switch is required. One embodiment of the invention has been constructed having a housing 11 with an axial dimension of approximately three-eighths of an inch, and an outside diameter of approximately thirteen-sixteenth of an inch, and a bimetallic disc of about one-half inch in diameter. Such a device may be readily adapted to have the open end of the housing abut an element (not illustrated), the heat content of which is to be controlled by the switch.

In the preferred embodiment, the contact disc 32 and the lamina 33 are constructed of low resistance gilding metal and silver, respectively. The silver lamina 33 is provided for the purpose of reducing the electrical resistance and rate of internal heating of the switch, so that a switch having relatively high current carrying capacity is provided. Accordingly, the low resistance contact disc 32 carries substantially all of the electrical current and very little passes through the bimetallic disc 28.

The preferred embodiment is constructed with the re tainer 29 having a portion of the finger-like projections 31 entirely preformed and the remaining portion partially preformed. After assembly of the retainer to the bimetallic disc and the contact disc, the remaining portions of the finger-like projections are formed in place.

The foregoing construction results in a switch having a bimetallic disc in which the force created by the flexing of the bimetallic disc is utilized solely to move the contact disc directly, none of the force being needed to overcome the resistance of intermediate members utilized in some prior constructions. Therefore, the bimetallic disc may be made as small as is possible to attain this mini- 1. In a snap-acting thermostatic switch, a base; stationary contact members carried thereby; a stud carried by said base; a snap-acting bimetallic disc centrally mounted I on said stud; a contact disc disposed at the side' of said bimetallic disc which faces the stationary contacts, said contact disc being concentric relative to the bimetallic disc and of approximately the same-diameter and engageable with the stationary contact members; and an annular member engaging the peripheral portion of the other side of the bimetallic disc, said annular member having fingers extending past the peripheral edges of the two ,discs and engaging the peripheral portion of the side of the contact disc facing the stationary contacts, said fingers being of such length and shape that they retain the peripheral portions of the two discs in engagement at all times, whereby warping or sagging of the bimetallic disc is prevented.

2. In a snap-acting thermostatic-switch, a base; a pair of spaced stationary contact members carried thereby; a stud extending from said base at right angles thereto midway between said stationary contact members; a con tact disc having a central opening therethrough through which said stud extends, said contact disc having a concentric annular boss projecting from one face thereof engageable with said pair of stationary contact members; a snap-acting bimetallic disc of approximately the same diameter as said contact disc fixed on the stud at the side of the contact disc away from the stationary contact members; and means for yieldingly retaining the peripheral portions of the two discs in engagement at all times, whereby warping or sagging of the bimetallic disc is prevented but rotation of the contact disc relative to the pair of stationary contacts is permitted, said retaining means comprising an annular member engaging the exposed peripheral portion of one of the discs and having a plurality of circumferentially-spaced resilient fingers extending past the peripheral edges of the engaging discs and yieldingly abutting the exposed peripheral portion of the other disc.

References Cited in the file of this patent UNITED STATES PATENTS 1,823,345 Britt Sept. 15, 1931 2,015,545 Bletz et al. Sept. 24, 1935 2,239,541 Spencer Apr. 22, 1941 2,434,984 Bolesky et al. Jan. 27, 1948 2,543,040 Mertler Feb. 27, 1951 2,622,169 Cataldo et al. Dec. 16, 1952 

